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Transition metal dichalcogenides (TMDs) benefit electrical devices with spin–orbit coupling and valley- and topology-related properties. However, TMD-based devices suffer from traps arising from defect sites inside the channel and the gate oxide interface. Deactivating them requires independent treatments, because the origins are dissimilar. This study introduces a single treatment to passivate defects in a multilayer MoS2FET. By applying back-gate bias, protons from an H–TFSI droplet are injected into the MoS2, penetrating deeply enough to reach the SiO2gate oxide. The characterizations employing low-temperature transport and deep-level transient spectroscopy (DLTS) studies reveal that the trap density of S vacancies in MoS2drops to the lowest detection level. The temperature-dependent mobility plot on the SiO2substrate resembles that of the h-BN substrate, implying that dangling bonds in SiO2are passivated. The carrier mobility on the SiO2substrate is enhanced by approximately 2200% after the injection.

We report that the anionic redox can occur in Ru-based layered-oxide-cathodes before full oxidation of Ru4+/Ru5+. Combining studies using first-principles calculation and experimental techniques reveals that further Na+deintercalation from P2-Na0.33[Mg0.33Ru0.67]O2is based on anionic oxidation after 0.33 mol Na+deintercalation from P2-Na0.67[Mg0.33Ru0.67]O2with cationic oxidation of Ru4+/Ru4.5+.

In the last few decades, numerous studies have focused on designing suitable hydrophilic materials to inhibit surface-induced fog or frost under extreme conditions. As fogging and condensation frosting on a film involves molecular interaction with water prior to forming discrete droplets on the surface, it is essential to control the extent of a film to strongly bind with water molecules for antifogging coatings. While the water contact angle measurement is commonly used to probe the hydrophilicity of a film, it oftentimes fails to predict the antifogging and antifrosting performance as this value only reflects the wettability of a given surface to water droplet. In this work, a polysaccharide-based film composed of chitosan (CHI) and carboxymethyl cellulose (CMC) is used as the model system and oligo(ethylene glycol) (OEG) moieties are additionally introduced to study the effect of OEG moieties on antifogging and condensation frosting. We show that the film containing OEG-grafted CHI exhibits excellent frost-resistant capability due to the OEG moieties in the film that serve as active sites for water molecules to strongly interact in a nonfreezable state.

Vacancy in the transition metal layer of sodium cathode material induces the formation lone-pair electrons in the O 2porbital.Material delivers more capacity from the oxygen redox validated by density functional calculation.Widened dominance of the OP4 phase without releasing O2gas.

Understanding metal-to-insulator phase transitions in solids has been a keystone not only for discovering novel physical phenomena in condensed matter physics but also for achieving scientific breakthroughs in materials science. In this work, we demonstrate that the transport properties (i.e., resistivity and transition temperature) in the metal-to-insulator transitions of perovskite nickelates are tunable via the epitaxial heterojunctions of LaNiO3and NdNiO3thin films. A mismatch in the oxygen coordination environment and interfacial octahedral coupling at the oxide heterointerface allows us to realize an exotic phase that is unattainable in the parent compound. With oxygen vacancy formation for strain accommodation, the topmost LaNiO3layer in LaNiO3/NdNiO3bilayer thin films is structurally engineered and it electrically undergoes a metal-to-insulator transition that does not appear in metallic LaNiO3. Modification of the NdNiO3template layer thickness provides an additional knob for tailoring the tilting angles of corner-connected NiO6octahedra and the linked transport characteristics further. Our approaches can be harnessed to tune physical properties in complex oxides and to realize exotic physical phenomena through oxide thin-film heterostructuring.

The electronic structure of an atomic-layer-deposited MoS2monolayer on SiO2was investigated using X-ray absorption spectroscopy (XAS) and synchrotron X-ray photoelectron spectroscopy (XPS). The angle-dependent evolution of the XAS spectra and the photon-energy-dependent evolution of the XPS spectra were analyzed in detail using an ab initio electronic structure simulation. Although similar to the theoretical spectra of an ideal free-standing MoS2ML, the experimental spectra exhibit features that are distinct from those of an ideal ML, which can be interpreted as a consequence of S–O van der Waals (vdW) interactions. The strong consensus among the experimental and theoretical spectra suggests that the vdW interactions between MoS2and adjacent SiO2layers can influence the electronic structure of the system, manifesting a substantial electronic interaction at the MoS2–SiO2interface.

Decrease in processing speed due to increased resistance and capacitance delay is a major obstacle for the down-scaling of electronics1–3. Minimizing the dimensions of interconnects (metal wires that connect different electronic components on a chip) is crucial for the miniaturization of devices. Interconnects are isolated from each other by non-conducting (dielectric) layers. So far, research has mostly focused on decreasing the resistance of scaled interconnects because integration of dielectrics using low-temperature deposition processes compatible with complementary metal–oxide–semiconductors is technically challenging. Interconnect isolation materials must have low relative dielectric constants (?values), serve as diffusion barriers against the migration of metal into semiconductors, and be thermally, chemically and mechanically stable. Specifically, the International Roadmap for Devices and Systems recommends4the development of dielectrics with ?values of less than 2 by 2028. Existing low-?materials (such as silicon oxide derivatives, organic compounds and aerogels) have ?values greater than 2 and poor thermo-mechanical properties5. Here we report three-nanometre-thick amorphous boron nitride films with ultralow ?values of 1.78 and 1.16 (close to that of air, ?= 1) at operation frequencies of 100 kilohertz and 1 megahertz, respectively. The films are mechanically and electrically robust, with a breakdown strength of 7.3 megavolts per centimetre, which exceeds requirements. Cross-sectional imaging reveals that amorphous boron nitride prevents the diffusion of cobalt atoms into silicon under very harsh conditions, in contrast to reference barriers. Our results demonstrate that amorphous boron nitride has excellent low-?dielectric characteristics for high-performance electronics.

In situexsolution of metal nanoparticles (NPs) is emerging as an alternative technique to deliver thermally stable and evenly dispersed metal NPs, which exhibit excellent adhesion with conducting perovskite oxide supports. Here we provide the first demonstration that Ni metal NPs with high areal density (∼175 μm–2) and fine size (∼38.65 nm) are exsolved from an A-site-deficient perovskite stannate support (La0.2Ba0.7Sn0.9Ni0.1O3−δ(LBSNO)). The NPs are strongly anchored and impart coking resistance, and the Ni-exsolved stannates show exceptionally high electrical conductivity (∼700 S·cm–1). The excellent conductivity is attributed to conduction between delocalized Sn 5s orbitals along with structural improvement toward ABO3stoichiometry in the stannate support. We also reveal that experimental conditions with strong interaction must be optimized to obtain Ni exsolution without degrading the perovskite stannate framework. Our finding suggests a unique process to induce the formation of metal NPs embedded in stannate with excellent electrical properties.

van der Waals (vdW) materials have shown unique electrical and optical properties depending on the thickness due to strong interlayer interaction and symmetry breaking at the monolayer level. In contrast, the study of electrical and tribological properties and their thickness-insensitivity of van der Waals oxides are lacking due to difficulties in the fabrication of high quality two-dimensional oxides and the investigation of nanoscale properties. Here we investigated various tribological and electrical properties, such as, friction, adhesion, work function, tunnel current, and dielectric constant, of the single-crystal α-MoO3nanosheets epitaxially grown on graphite by using atomic force microscopy. The friction of atomically smooth MoO3is rapidly saturated within a few layers. The thickness insensitivity of friction is due to very weak mechanical interlayer interaction. Similarly, work function (4.73 eV for 2 layers (hereafter denoted as L)) and dielectric constant (6 for 2L and 10.5–11 for >3L) of MoO3in MoO3showed thickness insensitivity due to weak interlayer coupling. Tunnel current measurements by conductive atomic force microscopy showed that even 2L MoO3of 1.4 nm is resistant to tunneling with a high dielectric strength of 14 MV/cm. The thickness-indifferent electrical properties of high dielectric constant and tunnel resistance by weak interlayer coupling and high crystallinity show a promise in the use of MoO3nanosheets for nanodevice applications.

Polymer dielectric materials with hydroxyl functionalities such as poly(4-vinylphenol) and poly(vinyl alcohol) have been utilized widely in organic thin-film transistors (OTFTs) because of their excellent insulating performance gained by hydroxyl-mediated cross-linking. However, the polar hydroxyl functionality also deleteriously affects the performance of OTFTs and significantly impairs the device stability. In this study, a sub-20 nm, high-kcopolymer dielectric with hydroxyl functionality, poly(2-hydroxyethyl acrylate-co-di(ethylene glycol) divinyl ether), was synthesized in the vapor phase via initiated chemical vapor deposition. The inherently dry environment offered by the vapor-phase polymer synthesis prompted the snuggling of polar hydroxyl functionalities into the bulk polymer film to form a molecular thin hydrophobic skin layer at its surface, verified by near-edge X-ray absorption fine structure analysis. The chemical composition of the copolymer dielectric was optimized systematically to achieve high dielectric constant (k≈ 6.2) as well as extremely low leakage current densities (less than 3 × 10–8A/cm2in the range of ±2 MV/cm) even with sub-20 nm thickness, leading to one of the highest capacitance (higher than 300 nF/cm2) achieved by a single polymer dielectric to date. Exploiting the structural advantage of the cross-linked high-kpolymer dielectric, high-performance OTFTs were obtained. Notably, the spontaneously formed molecular thin, hydrophobic skin layer in the copolymer film substantially suppressed the hysteresis in the transistor operation. The trap analysis also suggested the formation of bulk trap with a high energy barrier and sufficiently low trap densities at the semiconductor/dielectric interface, owing to the surface skin layer. Furthermore, the OTFTs with the −OH-containing copolymer dielectric showed an unprecedentedly excellent operational stability. No apparent OTFT degradation was observed up to 50 000 s of high constant voltage stress (corresponding to the applied electric field of 1.4 MV/cm) because of the markedly suppressed interfacial trap density by the hydrophobic skin layer, together with the current compensation by the bulk hydroxyl functionalities. We believe that the surface modification-free, one-step polymer dielectric synthetic strategy will provide a new insight into the design of polymer dielectric materials for high-performance, low-power soft electronic devices with high operational stability.

With increasing demand for transparent conducting electrodes, graphene has attracted considerable attention, owing to its high electrical conductivity, high transmittance, low reflectance, flexibility, and tunable work function. Two faces of single-layer graphene are indistinguishable in its nature, and this idea has not been doubted even in multilayered graphene (MLG) because it is difficult to separately characterize the front (first-born) and the rear face (last-born) of MLG by using conventional analysis tools, such as Raman and ultraviolet spectroscopy, scanning probe microscopy, and sheet resistance. In this paper, we report the striking difference of the emission pattern and performance of transparent organic light-emitting diodes (OLEDs) depending on the adopted face of MLG and show the resolved chemical and physical states of both faces by using depth-selected absorption spectroscopy. Our results strongly support that the interface property between two different materials rules over the bulk property in the driving performance of OLEDs.

Hydrogen, the smallest and the lightest atomic element, is reversibly incorporated into interstitial sites in vanadium dioxide (VO2), a correlated oxide with a 3d1electronic configuration, and induces electronic phase modulation. It is widely reported that low hydrogen concentrations stabilize the metallic phase, but the understanding of hydrogen in the high doping regime is limited. Here, we demonstrate that as many as two hydrogen atoms can be incorporated into each VO2unit cell, and that hydrogen is reversibly absorbed into, and released from, VO2without destroying its lattice framework. This hydrogenation process allows us to elucidate electronic phase modulation of vanadium oxyhydride, demonstrating two-step insulator (VO2)–metal (HxVO2)–insulator (HVO2) phase modulation during inter-integer d-band filling. Our finding suggests the possibility of reversible and dynamic control of topotactic phase modulation in VO2and opens up the potential application in proton-based Mottronics and novel hydrogen storage.

We firstly report an experimental visualization of a cycloaddition reaction on RT frozen asymmetric Si dimers. The frozen Si dimers with a local c(4 × 2) order were prepared by pinning flip-flopping Si dimers by using molecules. This RT pristine c(4 × 2) structure was used to determine what Si atom of an asymmetric Si dimer bonds to a molecule at the initial stage of the RT cycloaddition reaction, which has been a long-standing puzzling issue. This made it possible to compare directly experimental cycloaddition reactions with theoretical ones. As a prototype for the experiment, a 1,3-butadiene molecule adsorbed between Si dimer rows was used. The 1,3-butadiene molecule was found to prefer a symmetric Si pair on the frozen Si dimers, i.e., two electrophilic lower atoms of asymmetric Si dimers. This result is consistent with the theoretical prediction that a 1,3-diene molecule prefers a symmetric Si pair on the Si(001)c(4 × 2) surface. This experimental approach can also be applied to other studies for the adsorption of a molecule on a Si(001) surface at room temperature.

Highly pure monosheetsof graphene dispersible in water without the help of stabilizers have been prepared by photocatalytic reduction of graphene oxide using UV light and TiO2. More than 90 % of the highly conductive graphene was recovered in a pure form in solution, which showed no sign of aggregation even after one month (see figure).

The electronic structures of the interfaces between Au and poly(3-hexylthiophene) (P3HT) films with two different molecular orientations and orderings were investigated using synchrotron radiation photoemission spectroscopy. We found that, depending on whether thermal treatment was used, the P3HT thin film adopts two different molecular orientations, parallel and perpendicular to the silicon substrate, which result in different values of the vacuum level shift and hole-injection barrier. Thus, the molecular orientation and ordering of the P3HT material strongly affect the energy level alignment at the P3HT∕Auinterface.